On the Start screen, down in the lower right corner the minus sign and you'll zoom out to see all the groups of tiles. Right-click on a group and an option will come up below where you can rename the group. Type a name and you're good to go!

Really cool metro look. Can you share the trash and computer icon and the rainmeter weather widget too please?

The Computer icon is from a set of Token icons I got on Deviantart: Devine Icons. If you do a search for Devine Icons in the Customization > Icons > Dock Icons section, you'll be able to snag the whole collection (black also).Trash bin is from Token Icon set but I can't remember what the name was. Moded I think, but the blue ones. You can do a similar search for them also on DeviantartThe Rainmeter Skin is called 'My Skin' and it has all kinds of different widgets to put up. The clock I'm using is from the My Skin\Computer\Clock\12hr\clock_small.ini. I think I changed the font though to Segoe Semilight. I also got it from Deviantart.com